This invention relates generally to devices for joining segments of pipe and moving the joined pipe into an existing underground cavity. More particularly, the invention relates to mechanisms adjustable between engaging and non-engaging positions for moving pipe segments and for controlling the movement of pipe segments therethrough. The invention is of particular utility in connection with the replacement of water and sewer mains, although it can also be adapted for use in a wide variety of operations involving pipeline replacement, repair, and construction.
In pipeline replacement operations it is often impractical and infeasible to dig a trench along the entire length of the pipeline to be replaced. Instead, a trenchless method of pipeline replacement is used. In such a method, short access trenches are dug or existing manholes are employed at either end of the pipeline to be replaced. A pipe mole or the like is inserted, by way of one of the manholes, into the buried pipe. The pipe mole fractures the buried pipe into a series of fragments and displaces the fragments radially outwardly to create a void for the insertion of a replacement pipeline. As the pipe mole progresses along the length of the buried pipe, it tows behind it mated segments of the replacement pipe, placing the replacement pipe into position in the newly-created void.
In order to facilitate such a replacement operation, it is necessary to provide an apparatus for continuously feeding and joining new pipe segments to the trailing end of the replacement pipe as the pipe mole tows the replacement pipe into position. It is desirable that the apparatus be designed so as to fit into the manhole, where it can receive new segments of the replacement pipe and join them directly to the trailing end of the replacement pipe. Furthermore, the apparatus is preferably designed to be easy to disassemble, such that it can be conveniently transported to the job site, easily inserted into the manhole, and readily repaired or adjusted, if necessary, at the site.
It is also desirable to design the apparatus so that it minimizes axial recoil movement of the new segment of the replacement pipe. Such axial recoil is likely to be encountered when a new segment of pipe is mated to the trailing end of a buried replacement pipe. The buried replacement pipe can act as a spring when longer pipe lengths are reached. If not kept under compression, the pipe will yield when a new segment of pipe is joined.
Prior art devices for handling pipes have suffered certain deficiencies, particularly in the context of pipeline replacement operations. For example, while prior art devices have a variety of lever-actuated grip mechanisms or cooperating camming grip mechanisms for joining and moving pipe segments, such devices have not heretofore satisfactorily addressed the needs characteristic of pipeline replacement operations, such as recoil minimization, compactness, ease of installation, and ease of assembly.